U.S. Defense officials say three children held at the terrorist detention camp at Guantanamo Bay in Cuba have been released and returned to their home country.

The three children, aged 13 to 15, were seized in Afghanistan, two in raids on Taleban camps and the third while allegedly trying to obtain weapons to fight American forces.

Defense officials considered them enemy combatants who, despite their youth, had engaged in armed conflict or provided support to those fighting U.S. troops.

But the U.S. decision to imprison the juveniles with more than 600 other suspected al-Qaida and Taleban terrorist suspects at Guantanamo Bay stirred concern among international human rights groups when it was revealed last year.

The International Committee of the Red Cross said it did not consider Guantanamo to be an appropriate place to detain juveniles. Human Rights Watch called their detention a grave risk to their well-being.

U.S. officials say it was not easy to determine accurately the youths' ages and eventually required medical tests, including bone-density scans.

They say once authorities determined the three were children, they were separated from the other terrorist suspects and moved into their own housing. A Pentagon statement Thursday said they were provided an opportunity to learn math as well as reading and writing. They also received daily physical exercise.

The three are being resettled with the assistance of private relief groups. But the Pentagon says it is concerned Taleban or al-Qaida sympathizers may threaten their safety. That is why defense officials have not announced their names or issued any details on their release.

The release of the three children follows a visit to Washington earlier this month by Jakob Kellenberger, the President of the International Committee of the Red Cross, who met officials to discuss Guantanamo detainee issues.

Humanitarian groups, including the Red Cross, have also called for concessions for an undetermined number of other youths aged 16 and 17 held at Guantanamo who they say should be considered juveniles as well.

So far, 87 detainees have been released from Guantanamo. In addition four other detainees have been transferred to Saudi Arabia for continued detention there.